Molecular And Morphological Characterization Of Anopheles Melas Populations In Endemic And Non-Endemic Lymphatic Filariasis Communities In Coastal Ghana

ABSTRACT Several studies have revealed that towards the east of Accra, there is no lymphatic filariasis (LF) but it occurs to the west of Accra. Anopheles melas is known to be an efficient vector of LF and it occurs along the coastal part of Ghana, especially in estuarine areas. The present study therefore aimed at seeking explanation to why this different patterns of LF distribution occur along coastal Ghana. The hypothesis was that the eastern An. melas populations could be different from those occurring to the west of Accra at both morphological and molecular levels. At the molecular level, (cytochrome oxidase I (COI) ) gene sequences were analysed and at the morphological level the number of cibarial teeth were studied. Two sites representing communities to the east of Accra; Azizanya and Otropke in the Ga Adangme District and three communities; Asemko, Butre and Mpataano in the Ahanta West district were selected for the study. Pyrethriod spray catches was used to collect indoor mosquitoes. The mosquitoes obtained were morphologically identified as An. gambiae sensu lato and An. melas molecularly identified. Deoxyribonucleic acid (DNA) of each identified An. melas was then used as the template for COI analysis. Polymerase chain reaction products obtained were purified and shipped to Macrogen Inc. in the Netherlands for sequencing. Sequenced data was analysed using Bio Edit and MEGA V6 software for construction of phylogenetic trees as well as statistical inferences In-silico restriction enzyme digest of the sequences was done to determine restriction site differences between two An. melas populations. Similarity index was determined using Sørensen’s formula. Cibarial armatures of the two mosquito populations were compared using Student T-test. The study found no significant differences between the sequences of the two An. melas populations (Z-test of xvii neutrality = 0.33). Results of the phylogenetic analysis though not significant, revealed a geographic relationship only between two eastern populations clustering together, with Asemko branching off on a different node. Analysis of the in-silico showed eight mutational differences thus giving a QS value of 0.99. The restriction site analysis however revealed 16 unique site differences between them. The mean numbers (n, median and range) of cibarial teeth were 14.54 (n = 13, 15, 11 = 18) and 14.1 (n=13, 14, 11-19) for Azizanya and Asemko respectively, which were not statistically different (t=1.53, P = 0.14). In conclusion the two An. melas populations could be said to be similar in all aspects, however restriction enzyme differences could be potential markers for distinguishing the two populations. Further studies involving wider sampling of the areas and experiments with identified restriction enzymes should be undertaken to enable a firm conclusion to be drawn. Furthermore, to determine whether the eastern population are really refractory to W. bancrofti, xeno- experiments could be conducted using reared An. melas mosquitoes.